Attitudes toward direct predictive testing for the Huntington disease gene. Relevance for other adult-onset disorders. The Canadian Collaborative Group on Predictive Testing for Huntington Disease

Abstract

To assess attitudes toward, and projected utilization of, direct mutation testing by individuals at risk for Huntington disease (HD). Prior to the cloning of the gene for HD, a questionnaire concerning the use of a definitive test was constructed and mailed to 354 participants in the Canadian Collaborative Study for HD. Completed questionnaires were received from 250 participants (response rate, 71%). Persons were asked to indicate whether they would participate in a new predictive test that was either 100% accurate (the definitive test, requiring blood only from the proband) or only 99% accurate. Most (72%) of the persons who had previously received a result in a predictive testing program said they would request testing in either situation. Significantly more persons would request the definitive test than the 99% accurate test (72% vs 58%; P < .02). Respondents for whom testing was uninformative in the linkage test program or who had previously received an increased-risk result were more likely to indicate they would use the test than those who received a decreased-risk result or chose not to have the original test (P = .0003). Less than half (46%) of the participants who initially chose not to have the linkage test said they would return for the new direct test. The major factor that has limited acceptance of predictive testing for this group is the concern about receiving an increased-risk result in the absence of any therapy to alter progression of the disease. A direct mutation test for HD will most readily be accepted by persons who wanted but could not previously receive a result in the linkage test program and those who previously received an increased-risk result. In the absence of therapy, the majority of persons who previously chose not to have predictive testing are unlikely to participate in a new test despite improved accuracy. This has implications for the expected demands for testing services for other adult-onset genetic disorders.